Drive device for percussion drills, pile drivers and other rammers



June 21, 1966 P. GROSPAS 3,256,945

DRIVE DEVICE FOR PERCUSSION DRILLS, PILE DRIVERS AND OTHER RAMMERS Filed Dec. 4. 1963 2 Sheets-Sheet 1 Fig. I

PRIOR A R T June 21, 1966 P. GROSPAS 3,256,945

DRIVE DEVICE FOR PERCUSSION DRILLS, PILE DRIVERS AND OTHER RAMMERS Filed Dec. 4. 1963 2 Sheets-Sheet 2 United States Patent 917,686 9 Claims. (Cl. 17388) This invention concerns percussion drills, pile drivers, rock hammers and, in general, those machines, the action of. which results from the effect of impact of a rammer driven in a remote-controlled alternating motion.

The efficiency of such machines depends essentially, the rammers being equal, on the speed at which that rammer is driven the instant its impact is produced on the surface struck.

This invention specifically concerns a drive device which:

(l) .Enables the rammer to freely attain the maximum speed of which it is capable either at the end of free fall or at the end of fall accelerated by an auxiliary thrust, should it be subjected thereto;

(2) Assures lifting of the rammer gradually and without jolts by applying thereto an elastic force tending to balance exactly the resisting efforts opposing its rising motion, as well as gradual application of the stresses exerted on each of the elements in motion, regardless of the rate of stroke, and thus eliminates the jerks and overloads of the mechanism which occur on standard machines as'soon as they approach their critical speed.

To attain the results specified above, the drive device, which is the subject of the invention, is essentially characterized by the use, as the chief transmission, element, of a differential whose action is so combined that the parts driving the rammer are controlled, not directly and imperatively by the motor, but 'by the reactive effects of an adjustable elastic system which comes into play gradually, in proportion to the resisting efforts, and which serves also as a load limiting device Provision has further been made for safety devices protecting the mechanism from the jolts resulting from possible jamming of the rammer by limiting the stresses exerted on that mechanism to a predetermined acceptable value.

The following description explains clearly the fundamental advantages offered by the invention over the known prior art and describes, by way of non-limitative example, one embodiment thereof for operating a bit on .a percussion drill.

Reference will be made to the attached drawing in which:

FIGURE 1 is the diagram of a known device usually employed for the operation of drill bits.

FIG. 2 is a perspective view of one embodiment of the present invention showing the various elements constituting a driving device.

FIGURE 3 is a perspective view of the drive device represented on FIGURE 2, but equipped with a double elastic system.

FIGURE 4 is a longitudinal section of an element of the elastic system comprising a draw spring with pneumatic thrust and its means of adjustment.

FIGURE 5 is a longitudinal section of an apparatus identical to the foregoing (FIGURE 4) in structural principle, but using a compression spring.

Reference will be made first to FIGURE 1 where cable 1, at the end of which bit 2 is suspended, passes over suspension pulley 3 mounted in fixed position on upright 4 of the machine and leads to winch 5, which will be considered a fixed point, since it is operated only intermittent- 1y as the hole drilled goes deeper or to bring the bit back to the surface. Between winch 5 and suspension pulley 3 cable 1 passes over a guide pulley 6 and then over a working pulley 7 mounted at the end of a lever 8, the other end of which is connected'to shaft 9 of pulley 6, which is itself attached to general frame 10 of the machine.

Lever 8 is driven in a vertical alternating motion by a rod 11 connected to a crank 12 driven in continuous motion directly and imperatively by motor M. When, under the action of rod 11, lever 8 drops and the working pulley 7 resting on the cable lifts the bit 2. When lever 8 rises, the bit drops again at a speed directly proportional to the rate of rotation of crank 11.

In the example set forth, the rate of climb of the bit is the same as its rate of descent.

On recovery of the bit, the latter, acted on by its weight and the force of inertia resulting from the acceleration imparted to it, offers such resistance to motion that it is difficult to move it upward at a speed corresponding to its free fall velocity without subjecting the lifting mechanism to jolts andjerks inadmissable for proper maintenance of the machine.

It is therefore necessary to fall short of that optimum speed so that the impact of the bit is made at reduced speed with a considerable curtailment in effectiveness, number of strokes per unit of time and, therefore, in general efiiciency.

Furthermore, in case of. jamming of the bit while being acted on directly by the motor mechanism, violent stresses are exerted on the connection between the cable and the bit, on the cable itself and on lever and crank. Numerous mechanical breakdowns and breakages are due to such incidents. It will be seen below in our specifica- 3 wherein are found the working cable 1, bit 2, suspension pulley 3 and winch 5 shown in FIGURE 1 above.

FIGURES 2 and 3 show a differential 13, the well known internal composition of which has not been represented, such a device may take the form of the differential constituted by the elements 17-19 and 21-23 shown in the US. patent to Storer, Jr., et al., Patent No. 3,027,780, isued on April 3, 1962. In such an arrangement, the gears 17, 23, and 24 of Storer, J r. et a1. would be connected to the shafts M, 14 and 15, respectively, of the arrangements shown in FIGS. 2 and 3 of the present invention.

For the sake of clarity in the specifications, it will be assumed that the differential used is in a 1/1 ratio and that its planetary gearbox is driven at constant speed by The cranks operating the rammer and the elastic reac- 7 tion device may be driven respectively either by a planetary gearshift or by the planetary gearbox.

On the one hand, planetary gearshaft 14 bears crank 16 working the bit, crankpin 18 of which bears the pulley 20 operating the cable 1 resting on guide pulleys 22 and 23.

On the other hand, planetary gearshaft 15 bears crank 17 working the elastic device, crankpin 19 of which bears the pulley 21 operating on cable 24, one end of which is anchored to'a fixed point 29 and the other end connected to one of the ends of a draw spring 26, the other.

3 end of which is adjustably secured to frame B of the machine.

Standard operation of the general drive device is as follows:

Under the action of planetary gearbox rotating at constant speed V;

(a) Both shafts 14 and 15 are made to turn in the same direction as the latter;

(b) If equal resisting moments are applied in the same direction to each of cranks 16 and 17, shafts 14 and 15 will turn at speed V in the same direction;

(c) If one of the shafts is locked, the other will turn at speed 2 V;

(d) If one of the resisting moments grows faster than the other, the corresponding shaft will slow down, tending toward speed zero, and at the same time the other shaft will accelerate, tending toward speed 2 V.

By their rotation:

(a) shaft 14, crank 16, crankpin 18 and pulley 20 drive bit 2 in a vertical alternating motion by means of the cable 1 resting on pulleys 22 and 23;

(b) shaft 15, crank 17, crankpin 19 and pulley 21 stretch and relax spring 26 by means of the cable 24 resting on pulley 25 and fixed point 29.

The tension of spring 26 is such that the resisting moment opposite crank 17 prior to the instant of passage of its top dead center is greater than the moment applied to crank 16, so that crank 17 slows down and stops, while crank 16 accelerates and crosses its top dead center.

At that instant, the moment applied to crank 16, which was resisting, becomes aiding and tends to accelerate its rotary motion. Crank 17, which was stopped by its resisting moment, is at that same instant forced by the latter into reverse rotation. Through the internal action of the differential planetary gear, the rotation of shaft 14 and crank 16 is then thereby accelerated.

The principal turning moments, the moment applied to crank 17 and that applied to crank 16, are combined to accelerate rotation of the latter and release cable 1 and, therefore, bit 2, the rate of fall of which, linked to that of unwinding of cable 1, becomes independent of speed V of the motor system controlling the unit.

It has just been seen that in normal operation, on each complete turn of crank 16, crank 17 is shifted alternately between its bottom dead center and the neighborhood of its top dead center, barring incident.

So that crank 17 will stop in normal operation in a well-defined zone ahead of its top dead center, provision has been made to establish the elastic system through a combination of two elements, springs or others, one of which acts only after a given travel of the other, so that the resistance of the system suddenly increases at the instant corresponding to the position chosen for stopping of that crank 17. The preferred embodiment of such a system will be specified below with the aid of FIGURES 4 and 5.

When an incident such as jamming of the bit, for example, locks crank 16, crank 17 continues to turn, crossing its top dead center on each turn, which simply has the effect of periodically stretching and releasing spring 26 and, through the internal action of the planetary gear on shaft 14, crank 16 and cable 1, of driving the latter between its [complete release and a position of tension tending to make bit 2 rise.

The prior choice of force of spring 26 and of adjustment of maximum tension capable of being applied thereto through a complete rotation of crank 17 will control the limit of lifting stress applied to bit 2 by cable 1. The device acts in this case as a load limiting device and the rotation of crank 17 in complete turns is a clearly visible sign of trouble thanks to which the operator of the machine can immediately stop the latter and make the necessary adjustments.

For that purpose, automatic safety control can be applied by mounting on shaft 15 a cam 27 set up to act on a machine stop control the moment crank 17, going eyond its top limit of normal operation, crosses its top dead center.

The device represented on FIGURE 3 differs from the foregoing only in the substitution for single spring 26 of a set of two elastic elements 3030 adjustably connected to frame B of the machine and, on the other side, to the ends of cable 24, which is passed over pulleys 25, 21 and 28.

Operation is the same as in the foregoing case, but the travel of each of the springs or other elastic elements is cut in half, which facilitates their fabrication and durability when high power together with' rather long travel are needed.

Of course, instead of using springs, entirely pneumatic devices may be employed.

FIGURES 4 and 5 show mixed devices in which spring and pneumatic thrust actions are combined so as to make it possible to alter, during the operation of the machine, the conditions of control of crank 17 by opposing the maximum displacement of the spring with an elastic force which is rapidly adjustable at any time.

In FIGURE 4 apparatus 30a comprises a cylinder 45 in which a piston 33 can be moved, the hollow rod 31 of which is traversed by cable 24 connected to spring 3-8, the other end of said spring being adjustably fastened to the bottom of the cylinder at 39. The cable bears a part 40, the diameter of which is greater than the internal diameter of rod 31 and which, when the pull on spring 38 is sufficient, rests on piston 33.

Cylinder chamber 41 can communicate on one side with a compressed air source and on the other with the air through inlet and outlet tubes 34 and 35 equipped with valves controlled manually or by an automatic safety system, e.g., a decompression system controlled by means of cam 27.

The stroke of the piston, the rod 31 of which crosses stuifing box 46, is limited by lug 32.

Let us assume chamber 41 is filled with compressed air at suitable pressure by any outside source and cable 24 is loose. Piston 33 is then at the end of the stroke on the right and draw spring 38 itself is relaxed. When cab-1e 24- is drawn, it first undergoes the resistance of spring 38 which is stretched; then, with part 40 coming against the piston, the resistance of the latter is added to that of the spring. These arrangements make it possible to stop crank 17 at a well-defined point of its rotation.

The apparatus of FIGURE 5 differs from the foregoing only in that the spring 42 used is a compression spring taken between piston 33 and a plate 43 where the end of cable 24 is connected. On plate 43 there is connected a safety tube 44 the length of which is at least equal to that of spring 42 when the latter is totally compressed.

The piston must in principle remain immobile during normal operation to stop crank 17 before its top dead center.

The pressure in chamber 41 must therefore be such that it :balances the maximum rpull normally exerted on the spring by the cable. If the pull of the cable should accidentially become too strong, safety tube 44 leans, after limiting yielding of spring 42, on piston 33 which is shifted and crank 17 can pass its top dead center, as explainediabove.

What I claim is:

1. A drive device for a rammer, in which the lifting and release of the rammer are obtained by the action of a motor driven crank on a cable, said device comprising:

(a) a differential mechanism having a power input shaft and first and second rotating output shafts driven by said input shaft in such a way that the sum of the rotating speeds of said two outputs shafts will always be a direct linear function of the speed of said input'shaft;

(b) first crank means mounted on, and rotatably driven by, said first output shaft;

(c) first pulley means mounted on the free end of said first crank means;

((1) a first cable having one end fixed, the other end arranged for attachment to a rammer head, and an intermediate portion passing over said first pulley means, said first cable being mounted so that each full rotation of said first crank means causes said other end of said first cable to alternately ascend and descend;

(e) second crank means mounted on, and rotatabi driven by, said second output shafts; and

(f) elastic restraining means connected to the free end of said second crank means;

(g) the dome applied by said elastic restraining means varying directly with the displacement of said free end of said second crank from a reference position, said restraining means being adjusted so that; before said free end of said second crank reaches the position at which the force of said restraining means is a maximum, it produces a restraining force, which equals the largest reaction force normally encountered by said first pulley When it is in the process of lifting said end of said first cable, when a rammer head is attached thereto.

2. A device as recited in claim 1, wherein said elastic restraining means comprises a first elastic element having one end immovably connected to a fixed piece and a second cable having one end connected to the other end of said first elastic, element, said device further comprising a second pulley mounted on the free end of said second crank and having said second cable passing thereover.

3. A device as recited in claim 2 wherein the other end of said second cable is immovably connected to a fixed piece.

4. A device as recited in claim 2 wherein said elastic restraining means further comprises a second elastic element having one end immovably connected to a fixed 4 piece and its other end connected to the other end of said second cable.

5. A device as recited in claim 2, further comprising a guide pulley mounted for free rotation on a fixed support and guiding a section of said second cable, which section is located between the section passing over said second pulley and said one end of said second cable.

6. A device as recited in claim 2 wherein said first elastic element comprises two elastic members one of which adds its action to that of the other only when the force on the other goes beyond a predetermined limit, so as to cause the movement of said second crank means to be stopped at a predetermined distance from said reference position under normal operating conditions of the drive device.

7 A device as recited in claim 6 wherein one of said elastic members is constituted by a spring and the other of said elastic members is constituted by a regulatable, pneumatically operated piston.

8. A device as recited in claim 1, further comprising a cam rigidly mounted on said second shaft for indicating when said second crank goes beyond the position at which the force of said restraining means is a maximum.

9. A device as recited in claim 1 further comprising a pair of guide pulleys, each of which is situated to a respective side of the axis of said first output shaft, and a support pulley, both of said guide pulley and said support pulley being mounted to be freely rotatable on a fixed support, isaid first cable passing, in turn, around 7 one of said guide pulleys, said first pulley, the other of said guide pulleys, and said support pulley.

References Cited by the Examiner UNITED STATES PATENTS 0 MILTON KAUFMAN, Primary Examiner.

BROUGHTON G. DURHAM, Examiner. V D. FAULCONER, L. P. KESSLER, Assistant Examiners. 

1. A DRIVE DEVICE FOR A RAMMER, IN WHICH THE LIFTING AND RELEASE OF THE RAMMER ARE OBTAINED BY THE ACTION OF A MOTOR DRIVEN CRANK ON A CABLE, SAID DEVICE COMPRISING: (A) A DIFFERENTIAL MECHANISM HAVING A POWER INPUT SHAFT AND FIRST AND SECOND ROTATING OUTPUT SHAFTS DRIVEN BY SAID INPUT SHAFT IN SUCH A WAY THAT THE SUM OF THE ROTATING SPEEDS OF SAID TWO OUTPUTS SHAFTS WILL ALWAYS BE A DIRECT LINEAR FUNCTION OF THE SPEED OF SAID INPUT SHAFT; (B) FIRST CRANK MEANS MOUNTED ON, AND ROTATABLY DRIVEN BY, SAID FIRST OUTPUT SHAFT; (C) FIRST PULLEY MEANS MOUNTED ON THE FREE END OF SAID FIRST CRANK MEANS; (D) A FIRST CABLE HAVING ONE END FIXED, THE OTHER END ARRANGED FOR ATTACHMENT TO A RAMMER HEAD, AND AN INTERMEDIATE PORTION PASSING OVER SAID FIRST PULLEY MEANS, SAID FIRST CABLE BEING MOUNTED SO THAT EACH FULL ROTATION OF SAID FIRST CRANK MEANS CAUSES SAID OTHER END OF SAID FIRST CABLE TO ALTERNATELY ASCEND AND DESCEND; (E) SECOND CRANK MEANS MOUNTED ON, AND ROTATABLY DRIVEN BY, SAID SECOND OUTPUT SHAFTS; AND (F) ELASTIC RESTRAINING MEANS CONNECTED TO THE FREE END OF SAID SECOND CRANK MEANS; (G) THE FORCE APPLIED BY SAID ELASTIC RESTRAINING MEANS VARYING DIRECTLY WITH THE DISPLACEMENT OF SAID FREE EACH OF SAID SECOND CRANK FROM A REFERENCE POSITION, SAID RESTRAINING MEAN BEING ADJUSTED SO THAT; BEFORE SAID FREE END OF SAID SECOND CRANK REACHES THE POSITION AT WHICH THE FORCE OF SAID RESTRAINING MEANS IS A MAXIMUM, IT PRODUCES A RESTRAINING FORCE, WHICH EQUALS THE LARGEST REACTION FORCE NORMALLY ENCOUNTERED BY SAID FIRST PULLEY WHEN IT IS IN THE PROCESS OF LIFTING SAID END OF SAID FIRST CABLE, WHEN A RAMMER HEAD IS ATTACHED THERETO. 